Selective Detection of Ascorbic Acid Using Octacyanomolybdate‐Doped‐Glutaraldehyde‐Cross‐Linked Poly‐L‐Lysine Film Modified Glassy Carbon Electrode

Abstract

AbstractThe present work describes oxidation of ascorbic acid (AA) at octacyanomolybdate‐doped‐glutaraldehyde‐cross‐linked poly‐L‐lysine (PLL‐GA‐Mo(CN)$\rm{ {_{8}^{4-}}}$ film modified glassy carbon electrode in 0.1 M H2SO4. The modified electrode has been successfully prepared by means of electrostatically trapping Mo(CN)$\rm{ {_{8}^{4-}}}$ mediator in the cationic film of glutaraldehyde‐cross‐linked poly‐L‐lysine. The dependence of peak current of modified electrode in pure supporting indicates that the charge transfer in the film was a mixed process at low scan rates (5 to 200 mV s−1), and kinetically restrained at higher scan rates (200 to 1000 mV s−1). Cyclic voltammetry and rotating disk electrode (RDE) techniques are used to investigate the electrocatalytic oxidation of ascorbic acid and compared with its oxidation at bare and undoped PLL‐GA film coated electrodes. The rate constant of catalytic reaction k obtained from RDE analysis was found to be 9.5×105 cm3 mol−1 s−1. The analytical determination of ascorbic acid has been carried out using RDE technique over the physiological interest of ascorbic acid concentrations with a sensitivity of 75 μA mM−1. Amperometric estimation of AA in stirred solution shows a sensitivity of 15 μA mM−1 over the linear concentration range between 50 and 1200 μM. Interestingly, PLL‐GA‐Mo(CN)$\rm{ {_{8}^{4-}}}$ modified electrode facilitated the oxidation of ascorbic acid but not responded to other electroactive biomolecules such as dopamine, uric acid, NADH, glucose. This unique feature of PLL‐GA‐Mo(CN)$\rm{ {_{8}^{4-}}}$ modified electrode allowed for the development of a highly selective method for the determination of ascorbic acid in the presence of interferents.